18 



IxsTltrMKATS KMI'I.UYKM IV Sl.KDMXf!. 



The instruments generally taken on a sledge journey were a minimum thermometer and an aneroid. 

 Some parties earned a hypsometer, and the reading was taken once daily at the same time as the aneroid 

 was used. I would suggest, for future guidance, that some indication should be given of what is wanted 

 to be done at these secondary stations, which must necessarily be moving stations, and that instruments 

 should be supplied for sledging purposes only; an aspirator would, I think, be a good and useful 

 instrument, and also a minimum thermometer. 



I strongly recommend the hypsometer, provided the observations are useful. The work of boiling and 

 getting a reading is small, and can easily be done whilst the observer is waiting for the pot to boil at the 

 meal hours. The question of weight has to be considered, as it is a most important factor in the work; 

 and the sum total of instruments forms already a large proportion of the equipment in sledge journeys. 



The work of observing is easily performed, as the whole set of observations docs not take more than a 

 few minutes. Two-hourly readings can easily be obtained. 



NOTES TO ILLUSTRATIONS OF SOLAR AND CLOUD PHENOMENA, 



BY 



EDWARD A. WILSON, M.B. 



Plate I. Solar phenomenon observed on the Great Ice Barrier, November 29, 1902. 4 P.M., appt. time. 

 S. lat. 80 30', E. long. 165. Wind S.S.W., force 1, driving showers of ice crystals. Blue sky with cirro- 

 stratus rapidly crossing to the N.E. A white fog-bank lay on the horizon persisting up to 30 of altitude. 

 A complete ring or band of white light ran horizontally through the Sun (altitude 27). In this ring, 

 dividing its circumference into three equal parts, appear the Sun and two luminous white mock-suns. 

 Round the Sun was a Solar halo of prismatic colour with small arcs of intense prismatic colour outside it, 

 on a level with the Sun. The blue of the sky within the halo was considerably darker than the blue 

 outside. Immediately below the Sun on the horizon was a luminous white mock-sun. In a vertical 

 line above the Sun -close to the zenith, and forming part of a small circle with zenith for centre-- was an 

 exceedingly brilliant arc of prismatic colour, set in the deep blue of the sky. The following measurements 

 were taken by Captain SCOTT : Altitude of Mock-suns, Sun, and white band of light L'7 above the horizon. 

 Bearing of "White Mock-suns" 120 from one another. Diameter of Solar halo 54. Radius of upper 

 prismatic arc (centre = zenith), 7. Fr.-cir.-str. rapidly cleared away as phenomenon appeared, leaving 

 clear blue sky overhead down to within 30 of horizon, where white fog-bank or low stratus persisted. 



Plate II. Solar phenomenon observed on the Great Ice Barrier, December 16, 1902. 1 A.M. S. lat. 

 80 45', E. long. 1G2 . Driving showers of ice crystals. Southerly breeze, force 1-2. Low driving 

 stratus clouds in patches, breaking occasionally to expose clear blue sky and fracto-cirro-stratus. The 

 white mock-suns seen on November 29th were occasionally visible, but were not connected by the 

 horizontal band of white light. There was much more drifting cloud this day than on November 29th, 

 and much less blue sky visible. The difference in depth of blue colour between the sky inclosed by the 

 Solar halo and that outside it was not noticeable, owing to the fact that a white mistiness obscured the 

 blue of the sky almost all over the Sun's quarter (S). Z, zenith; u, broad prismatic arc; b, narrower ditto. 



Plate III. Solar phenomenon observed on the Great Ice Barrier, December 29, 1902. 2 P.M. S. lat. 

 82 17'. The most brilliant and the broadest bands of prismatic colour were those at / and at the four 

 points on the Sun's completed halo. The halo itself was neither broad nor brilliant. The horn-shaped 

 band was at times very bright and moved round the halo with a change in the position of observer's 

 eyes. The white mock-suns on the north, south-east, and south-westerly horizon were large and bright 

 and dome-shaped. The zenith-centred smaller white circle and the detached white arcs in the south 

 appeared only for a few moments and were never very pronounced. The sky was blue and all the drift 



